Generally, CNC lathes and the like are provided with a plurality of spindles and a plurality of tool posts and machine a plurality of workpieces with a plurality of tools to increase the machining speed thereof.
In these CNC lathes, the spindles are fixedly coupled to the tool posts, and thus machining can be carried out, for example, only by a first spindle coupled to a first tool post and a second spindle coupled to a second tool post.
Consequently, although a plurality of the spindles are provided, there is a limit to the effective machine of the workpieces at a high speed. For example, when the machining of a first workpiece takes a long time but a second workpiece is machined in a short time, the machining can be effectively carried out in such a manner that the first workpiece is partially machined by the second tool post.
Further, sometimes a requirement for machining a workpiece mounted on a second spindle by a tool mounted on a first tool post arises, depending on the structure of a machine.